Sandbox 252

Designing a Physical Model to Tell the Story of Acetylcholinesterase
Reflected in our design are two key concepts of AChE: the biochemistry of how the ACh overcomes the depth of the active site gorge before hydrolysis can occur, and how a toxin inhibits the substrate from finding the active site.Two physical models were designed and made by 3-dimensional printing technology: Torpedo californica (Tc) AChE in complex with a modeled ACh ligand, and Tc AChE in complex with FAS-II. Both models were based on protein data bank (PDB) files, and Rasmol computer modeling program. PDB files included PDB entry code 2ace for the TcAChE/ACh complex, and PDB entry code 1fss for the Tc AChE/FAS-II complex.



Features of the Substrate Traffic Story: AChE/ACh
AChE is an alpha/beta hydrolase fold with an amino acid sequence of 4-535. The alpha carbon backbone of AChE has ? alpha helices and ? beta sheets.

The 14 aromatic residues that line the active site gorge are tyr70, trp84, trp120, tyr121, tyr130, trp233, trp279, phe288, phe290, phe330, phe331, tyr334, trp432 and tyr442.

The Catalytic Triad or active site includes glu327, his440 and ser200. Here is where Acetylcholine is hydrolyzed.

Three of the aromatic residues that line the gorge attract the quaternary ammonium ion of ACh. These 3 aromatic residues, trp279, tyr70, and tyr121, sit at the entrance of the gorge and make up the Peripheral Anionic Site.

Two of the 14 aromatic residues lining the active site gorge that are considered significant for holding ACh in an optimal position for hydrolysis are trp84 and phe330. These residues form the Catalytic Anionic Site.



Features of the Inhibition Story
FAS-II amino acids 1-61 were illustrated in an alpha carbon backbone. The alpha carbon backbone of FAS-II has 4 beta sheets forming three loops or fingers. The residues Thr8, Arg27, Met33 and Val34 are present on two loops of the toxin FAS-II.

When FAS-II binds to AChE, Arg27 and Met33 interact with trp279 of the Peripheral Anionic Site, while Val34 and Thr8 interact with tyr70 of the Peripheral Anionic Site.